We usually install a two-board "picture frame" border on most of our projects.
Besides being aesthetically pleasing, it also covers the top edge of the deck fascia board preventing dirt and debris from building up in the gap.
Greg DiBernardo of Bergen Decks explains the three main types of synthetic decking available on the market today. You may be surprised to know that "composite" decking is only one type of synthetic decking and it is being phased out by better, more modern